Air jet process and apparatus for making novelty yarn and product thereof



0d 23.1969 M. G. K,.JoARD:-:R ETAL 3,474,613

AIR JET PROCESS AND APPARATUS FOR MAKING NOVELTY uns mu Pnonucr Trimmer Filed sept. 13. 1968 United States Patent O 3,474,613 AIR JET PROCESS AND APPARATUS FOR MAKING NOVELTY YARN AND PRODUCT THEREOF Mohammad Golam Kiln-ia Joarder, Newark, Del., and Garland Ray Walker, Chattanooga, Tenn., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Continuation-in-part of application Ser. No. 671,641, Sept. 29, 1967. This application Sept. 13, 1968, Ser. No. 785,832

Int. Cl. DIh 13/26; D02g 3/02, 3/00 U.S. Cl. 57--34 10 Claims ABSTRACT OF THE DISCLOSURE A process and apparatus for producing a novel Slubbed yarn wherein a multifilament yarn is forwarded in a first high velocity fluid stream against one area of a foraminous member and is withdrawn through a turbulent fluid zone formed by the interaction between the first fluid stream and a second high velocity fluid stream directed against the foraminous member adjacent the first fluid stream. The areas of fluid stream contact on the foraminous member have different porosities.

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our pending application Ser. No. 671,641 filed Sept. 29, 1967, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a novel Slubbed yarn and, in particular, to a process and `apparatus for producing a slubbed yarn of continuous, synthetic filaments.

Slubbed yarns are characterized by having enlarged, stable segments along their length and have found wide use in the textile industry because of interesting surface effects in the fabrics prepared from them. While suitable for many purposes, Slubbed yarns of the prior art have been found to be deficient in one or more aspects related to repetitive patterning due to periodicity of slub length, thickness or frequency, poor performance in thel conversion to fabric due to inferior yarn strength, or failure to impart to the fabric the desired appearance and handle because of a lack of essential properties in the yarn.

The present invention provides an improved slub yarn for the production of novelty fabrics. By the use of this invention, novelty fabrics are obtained that are devoid of patterning, have a broad range of aesthetic appeal and can be prepared in a relatively efiicient manner.

SUMMARY OF THE INVENTION It has now been found that the deficiencies of prior art yarns can be largely overcome by providing a synthetic, continuous-filament, Slubbed yarn having a random distribution of slubs formed by entanglement of filaments and yarn loops and prepared from a diamine having the formula R M @ltlg NH. Lil. R R

3 ,4 74,6 l 3 Patented Oct. 28, 1969 ice provide synthetic novelty fabrics of a class heretofore unobtainable.

The slubbed yarns of this invention can be prepared by known processes, eg., as taught in U.S. Patents 3,296,- 785 and 3,116,589. In a preferred process for preparing these novel Slubbed yarns, a continuous-filament yarn is continuously supplied to a feed jet from a suitable source, such as a spinning position or a supply package, and forwarded by the jet in a high velocity stream of compressible fiuid to impinge against the upper surface of a screen or like foraminous member. A second jet directs a high velocity stream of compressible iiuid against the screen in the vicinity of the stream from the feed jet. The impinging streams create turbulent conditions which aid slub formation. The yarn is withdrawn from the upper surface of the screen at a rate at least about 5% less than the feed rate. A slub is initiated in the overfed supply of yarn and a mass of yarn containing entangled filaments and yarn loops is withdrawn into the second, or slubbing, jet counter-current to the jet stream fiow and the entangled mass consolidated into `a slub. If a carrier yarn is used it may be introduced at any convenient location, but will preferably be introduced prior to the eXit of the slubbing jet. If the slubbing jet is of the interlace type, the carrier yarn will be introduced in the slubbing jet so as to provide a more integral combination of the slubbed yarn and the carrier yarn. The combined yarns will then preferably be treated as taught in U.S. Patent 3,296,785 so as to provide a more weavable yarn by treating them in third and fourth jets of the interlace and torque type. Suitable conditions and apparatus are described in the above-identified patents.

In the slub-forming system of this process, the surprising discovery has been made that the addition of a flow restricting element to the lower surface of the screen that coincides with the area where the yarn is deposited by the feed jet, can significantly alter the distribution of the slubs.

The element may be impervious, but preferably will have varying degrees of porosity dependent on process conditions to be established and the yarn characteristics desired. However, in all cases the effect of the element is to lower or decrease the porosity of the screen at the location where the yarn is deposited. When an interlaced yarn is to be Slubbed, it is highly desirable, if' not necessary, that the yarn be forwarded by the feed jet to the surface of a relatively porous screen (e.g., 36% open area) afxed to a disc, or other flow-restricting element, containing a relatively small number of openings.

The preferred embodiment of the slub-forming system provides a new method for the significant alteration of the slub distribution of randomly-formed slubs in continu0usfilament yarns. By forwarding the yarn with a high velocity stream of a compressible liuid towards a screen, or screenlike, surface which provides the yarn contact surface of a multiple component assembly, the number of slubs formed in a continuous-filament yarn can be increased substantially, eg., 10% and more. This method allows the yarn to be separated from the fluid while providing, at the same time, an atmosphere more conducive to slub initiation. It is postulated that as the yarn and the compressible fluid pass towards the assembly, the yarn is deposited `at the surface of the screen and the fluid passes on through and a portion of it strikes the surface of the flow restricting elcment and is deflected back through the screen while the remainder exits from the assembly. The defiection of a portion of' the fluid back into the locality to which yarn is being forwarded results in the formation of a zone of deflective turbulence which is a much more favorable fiuid turbulent zone for slub formation than provided by prior art apparatus. As will be apparent, additional surfaces may be provided so that the yarn is forwarded to 'an assembly having a multiplicity of surfaces. However, in practice, it has been found that satisfactory changesl can usually be obtained by varying the porosity of the flow restricting surface. This preferred embodiment can, of course, be used with synthetic yarns other than those described herein above, such as other polyamide yarns, polyester yarns, cellulose acetate yarns, and the like.

The weaving performance of slubbed yarns is invariably poorer than comparable unslubbed yarns under the same weaving conditions. This differential in performance is due to the propensity of the slubs to hang up when contacting other surfaces with a resulting increase in yarn breakage in weaving. In the formation of slubbed yarn from continuous-filament yarns as taught herein, the strength of the slubbed yarn relative to the unslubbed yarn is reduced and hence the weaving performance of such yarns deteriorate to a greater extent than would otherwise be the case. The decrease in strength of the slubbed yarn is attributed to a reduction in the loadsupporting filaments at an end of the slub and/or to the formation of knots. In some situations, it is possible to partially alleviate this disadvantage by decreasing the slub thickness, but this approach is quite limited since it also decreases the contrast that the slubbed yarn was initially chosen to provide. It now has been found, surprisingly, that in the practice of a preferred embodiment of this invention, continuous-filament slubbed yarns are provided which have an improved Weaving performance and good contrast.

Pleasing fabrics from slubbed yarns are obtained when the yarns contain a high slub frequency, an appreciable slub length, a large number of slubs having a denier ratio about -10 times that of the yarn from which the slubs are formed and a small number of slubs having `sections wherein the denier ratio is greater than 25. Accordingly, there is provided a continuous-filament slubbed yarn characterized by having at least 120 slubs per 1,000 yards (9l4 meters) with Ztl-95% of the slubs having a segment with a denier ratio greater than about 7, 0 to of the slubs having a segment with a denier ratio greater than about 2S and less than 3% of the slubs having a segment with a denier ratio greater than about 40. These novel slubbed yarns provide the required contrast by having a large number of thick slubs and at the same time significantly improve weaving performance despite the problems imposed on continuous-filament slubbed yarns.

The term slub as used herein refers to a readily discernable, stable enlargement of the base yarn having a length of at least 0.64 centimeter. Smaller enlargements on the base yarn are difiicult to evaluate and make no contribution to the present invention.

DESCRIPTION OF THE DRAWING The drawing is a diagrammatic representation of a preferred embodiment of process and apparatus for preparation of the yarn of this invention, the jet devices being shown in cross-section taken through the yarn passageways.

The drawing shows a multifilament yarn 1 being Withdrawn from supply package 2 through pigtail guide 3 and over snub guide 4 to feed rolls 5 and 6. Passage of the yarn through the nip of rubber-covered idler roll 5 and driven feed roll 6 provides positive control of the feed rate. If desired, the yarn may be wetted as with a water wick as shown by the dotted line at 28. The yarn then passes through feed jet 7 and is forwarded by air introduced into the jet through fitting 8 to form a highvelocity stream. The yarn is forwarded to strike against the upper surface of a screen 9, positioned across the path of the air stream at an angle of about 90, so that the yarn is deposited on one area of the screen and the air passes through the screen. A second screen 29 is positioned adjacent to the lower surface of screen 9 coincident with the yarn-depositing area and serves as a ow restricting element. A slubbing-jet 10 of the interlacing type for consolidating slubs in the yarn is supplied with air under pressure through fitting 11 to form a second high velocity stream which is also directed perpendicularly against the screen 9 to impinge on the screen adjacent to the stream from the feed jet forming a turbulent iiuid zone between the streams. Preferably the screen 9 is completely enclosed at the sides and top to form a box-like enclosure 12 which contains the yarn in the turbulent area during slub formation. The sides and top may be of any material which will retain the yarn, either perforated or solid, such as screening, plastic or sheet metal, the feed jet and the slubbng jet being mounted in the top of the box-like enclosure, the yarn passes from the screen through slubbing jet 10 in a direction counter to the high velocity stream passing through this jet. A carrier yarn 13, from package 14, passes through pigtail guide 15 and over snub guide 16, and enters the side of jet 10 through an opening 17. The slub yarn and carrier yarn pass from the jet 10 around roller guide 18 to a ply interlacing jet 19, supplied with air under pressure through fitting 20, and is false twisted by passing through torque jet 21 supplied with air under pressure through fitting 22. The plied yarn then passes through a pigtail guide 24 and U guide 25 to a conventional windup such as a package 26 surface driven by self-traversing drive roll 27.

The novel slubbed yarns of this invention are characterized by a broad range of slub size with the slubs being distributed at random along the length of the yarn. This randomness of size and location is a distinct advantage when the yarn is woven into a fabric. The number of slubs in the yarn will vary, but preferably there will be at least l0 slubs per 1,000 yards (per 914 meters) of yarn. Except when the slubs are mostly small slubs, the number of slubs cannot be expected to exceed about 1,200 slubs per 1,000 yards (per 914 meters) of yarn. For many textile purposes, yarns having, for each 1,000 yards (914 meters) about 12 to about 500 slubs will be suitable, and those having about 50 to labout 350 especially so. It is preferred that at least one of the slubs have a length of at least 5 inches (12.7 centimeters) and the length of the slubs may range upwards to inches (254 centimeters) and more. Preferred yarns will have an average slub length of at least about 1 inch (2.54 centimeters). If desired, the slubbed yarns may be combined to form a plied yarn.

The measure of slub thickness used herein is the denier ratio, i.e., the ratio of the denier of the slub to the denier of the yarn from which the slub is produced. Since the slub bulk can result from both filament entanglement, i.e., one or more of filaments of the yarn bundle, and yarn entanglement, Le., a loop of yarn involving all of the filaments of the yarn bundle as a more or less unitary mass, the thickness of the slubs, or segments of them, can vary over a wide range. Filament entanglement can produce a slub segment having a denier ratio of about 1.1 up to about 3.0. Slub segments involving a yarn loop will have a denier ratio of at least 3. Since the denier ratio for a given slub is an average Value, most slubs will have a. denier ratio of at least about 2.0. Where extensive yarn looping is involved, the denier ratio of the slub may exceed 25. Preferably, the average denier ratio for slubbed yarn will be from about 3 to about 20.

The slubbed yarns of this invention may be characterized by a manual operation or by the use of equipment designed to make various length and thickness measurements on the slubs of the yarn. Based on both kinds of measurements, it is believed that the two measurements will not differ from each other by more than about 10 percent. One suitable apparatus is referred to as a Slub Analyser and, as used herein, counts, for each 1,000 yards (914 meters), all of the slubs having a length greater than 0.25 inch (0.64 centimeter), greater than 10 inches (25.4 centimeters), greater than 50 inches (127 feed rate-withdrawal rate Overf eed Withdrawal rate The preferred novel yarns of this invention are produced from fiber-forming polyamides prepared from the bis(4aminocyclohexyl) alkanes and saturated dibasic acids having 9 to 16 carbon atoms in a straight chain. Preferably, the acid will be dodecanedioic acid and the polymer will be prepared using 40-l00%, preferably 70-100%, of the trans-trans stereoisomer of bis(4amino cyclohexyl) methane. The polyamide will have a molecular weight of at least 8,000, and preferably at least 15,000. The yarn is characterized by a high level of tensile properties at both room and elevated temperatures, outstanding stain resistance and excellent dimensional stability over a broad range of conditions.

Preferably, the yarn to be treated is a continuousmultifilament yarn at zero twist. Interlaced yarns may also be used, e.g., a yarn having a distance of 14 centimeters between interlace nodes is readly converted into a slubbed yarn.

The feed yarns may have filaments with various crosssections, such as round, trilobal, cruciform and the like. Mixed shrinkage yarns may be used or the carrier may be a mixed shrinkage yarn. A preferred embodiment is a mixed-shrinkage yarn comprising a mixture of homopolymer filaments prepared from bis(4aminocyclohexyl) methane containing 70% of the trans-trans stereoisomer and dodecanedioic acid and copolymer filaments prepared from the diamine of the homopolymer and a mixture of dodecanedioic and isophthalic acids such that about by weight, of the copolymer is due to isophthalate units.

Also, a carrier yarn of a different polymer type may be used to provide, for instance, cross-dyeing effects.

Example I A homopolymer is prepared in an autoclave from the salt of bis(4-aminocyclohexyl)methane and dodecanedioic acid in a standard manner. The diamine contains about 70% of the trans-trans stereoisomer. Similarly, a copolymer is prepared except that isophthalic acid is substituted for a portion of the dodecanedioic acid used. Sufficient isophthalic acid is used so that the isophthalate units account for 10%, by weight, of the copolymer. The homopolymer and the copolymer are melted separately and cospun as a SLi-filament yarn having filaments with a trilobal cross-section. The yarn is drawn in the usual manner, interlaced and wound to a package.

Apparatus similar to that shown in the drawing is used to prepare a slubbed yarn and combine it with a carrier yarn. The interlaced yarn described above is fed to the feed jet at I572 yards per minute (523 meters per minute) and the subsequently slubbed yarn wound up at 520 yards per minute (475 meters per minute) so as to provide for an overfeed of 10.0%. The feed jet forwards the yarn to a 40 x 40 mesh screen of 0.025 centimeter diameter wire. A plastic disc 2 inches (5.08 centimeters) in diameter and containing 8 spaced holes 0.25 inch (0.64 centimeter) in diameter is adhered to the bottom of the screen directly under the feed jet. The yarn is removed from the feed zone and passes through the slubbing jet in a countercurrent direction. A second package of the above-described supply yarn is provided as the source of the carrier yarn that enters the slubbing jet where it is combined with the slubbed yarn. Air pressures for the feed and slubbing jets are 10 and 40 pounds per square inch (0.7 and 2.8 kilograms per square centimeter) gage, respectively. The combined slubbed and carrier yarn is passed to the third, or ply-interlacing, jet and then to the four, or torque, jet, after which it is wound to a package. 'Ihe air pressure in the third and fourth jets is 60 pounds per square inch (4.2 kilograms per square centimeter) gage.

Two sections of the slubbed yarn produced above, each 1,000 yards (914 meters) in length, are characterized with a Slub Analyser. The number of slubs is found to be 269 in one section and 247 in the other, with the number greater than 10 inches (25.4 centimeters) in length being 3 and 5. Three of the slubs in each of the sections exceed 50 inches (127 centimeters) in length, and the section having the fewer slubs has 1 slub larger than 100 inches (254 centimeters). One section is found to contain 146 (54.3%) and the other 147 (59.5%) slubs having a segment with a denier greater than 440 (denier ratio 7.3). Of the slubs in each section, 13 (4.8% for 269 and 5.3% for 247) have a segment with a denier greater than 1,440 (denier ratio 24), and 1 (0.37% for 269 and 0.4% for 247) having a segment with a denier greater than 2,440. In the section having the greater number of slubs the average slub length is determined to be 4.7 inches (11.9 centimeters) in length and the average denier ratio is calculated to be 3.8; for the other section, the corresponding values are an average length of 5.1 inches (13.0 centimeters) and average denier ratio of 3.9.

A warp is prepared from a polyhexamethylene adipamide yarn having 34 filaments and a denier of 70. This warp is used in the preparation of a fabric with various slubbed yarns as the filling so that the weaving potential of the slubbed yarns can be determined under identical conditions. The yarns are converted to a plain weave fabric having Warp ends per inch (35.4 warp ends pe-r centimeter) and 58 filling ends per inch (22.8 filling ends per centimeter) and the number of loom stops per yard (meter) due to the filling yarn is recorded for the weaving of a minimum of 10 yards (9.14 meters) of fabric. Using this procedure, the slubbed yarn described above is woven to fabric with only 0.2 break per yard (0.22 break per meter). Using the same procedure, silk yarns containing slubs, i.e., doupioni silk yarns, from a variety of sources are woven to fabric with 0.5-2.0 breaks per yard (0.55 to 2.2 breaks per meter). A commercially available cellulose acetate slubbed yarn and a commercially available polyester slubbed yarn are also evaluated with this procedure and also found to weave with a relatively high incidence of breaks.

Example II Apparatus similar to that of Example I is set-up so as to provide two positions, I and II, for producing a slubbed yarn from a drawn interlaced yarn similar to that described in Example I. A -total of 8 runs are made as 4 pairs, A, B, C, D with A and C being made on position I and B and D on position II. The runs of each pair are made under the same conditions, except that the first run (e.g., A1) is made without a disc and the second run (e.g., A2) with a disc. The disc used is the same as that for Example I except for A2 where the disc has no holes. For A and B an overfeed of 12.4% is used with A having a distance of 1.125 inches (2.86 centimeters) between the bottom of the feed jet and the screen, and B a distance of 0.5 inch (1.77 centimeters). For both C and D, overfeed is 10.2% and the distance between the feed jet and the screen is 1.125 inches (2.86 centimeters). In all other aspects, the 8 runs are made as in Example I. The characteristics of the slubbed yarn obtained in the 8 runs is given in the table.

TABLE I Run A1 A2 B1 B2 C 1 C2 D1 D 2 Slub Length, N o. of slubs greater than:

0.25 inch 158 269 158 220 184 244 181 242 10 inches.. 34 16 45 1 32 21 25 21 50 inches 0 0 0 0 0 0 0 0 100 inches 0 0 0 0 0 0 0 0 Slub Thickness, N of slubs greater than:

7.3 146 244 141 108 9 112 99 100 (92. 5%) (90. 7%) (S9. 3%) (49. 0%) (5o. 5%) (46%) (54. 7%) (45%) 24. 0 3 23 10 2 7 24 16 40 7 (21. 57) (8. 59%) (12. 0740) (0.919217) (8. 15%) (2. 97g) (13. 37g) (6. 6%) (s. 8%) (o. 31%) (2. 5%) (o. 45%) (a sfo) (o. 8%) (4. 0%) (o. 4%) Loom Stops/Yd 1. 6 0. 2 1. 0 0. O

Exampie III Apparatus similar to that of Example 1 is set up for producing a slubbed yarn from a 60-denier drawn interlaced yarn similar to that described in Example I.

The yarn overfeed is 10.22 percent, A plastic disc 2 inches (5.08 centimeters) in diameter and containing 41 spaced holes 0.094 inch (0.24 centimeter) in diameter is adhered to the bottom of the screen directly under the feed jet. The feed jet is 1 inch (2.54 centimeters) above the screen. The yarn is removed from the feed zone and passes through the slubbing jet in a counter-current direction. A second package of the above-described supply yarn is provided as the source of the carrier yarn that enters the slubbing jet where it is combined with the slubbed yarn. Air pressure for the feed and slubbing jets are 17 and 40 pounds per square inch (1.2 and 2.8 kilograms per square centimeter) gage, respectively. The combined siubbed and carrier yarn is passed to the third, or torque, jet and then to the fourth, or ply interlacing jet, after Which it is wound to a package. The air pressure in the third and fourth jets is 60 pounds per square inch (4.2 kilograms per square centimeter) gage.

The apparatus is operated for 2 days and produces 16 packages Weighing approximately 2.5 pounds (1 kilogram) each. Two sections of each package, each 1,000 yards (914 meters) in length are characterized with a Slub Analyzer. The number of slubs and the number of thick slubs is averaged for each package and the percentage calculated. The characteristics of the slubbed yarn is shown in Table II.

TABLE II Slub Length-No. of slubs greater thanratio greater than- Package 0.25 10 50 100 No. (in.) (in.) (in.) (in.) 7.3 Percent 24.0 Percent 40.7 Percent 1 te a s s .at 00 t 00 a 00 2 e a t s s 00 s 00 :s 0

a a a t s e 0000 s 00 i 00 4 a s t s 00 00 00 5 a s i s .at 00 a 00 00 E a a s s a 00 12 00 t 00 Y a a s s a 00 2 00 s 0 8 at it s s a 00.0 00 i 00 Q te a s s s 000 2 00 s 00 10 a a s s s 00 t 00 t 00 11 is s s 2 a 00 .t 00 s 00 12 is a s s 23 0000 .t 00 s 00 a 3 t s 0000 s 0.0 i 00 14 -0 a s s s s 00 00 a 00 is t a .e 00 a 00 i 00 1G e s s s 00 t 00 i 00 The slubbed yarns of this invention can also be used 4as the warp yarn as well as the filling yarn. For instance, a 2 x 2 twill fabric is readily produced using a slubbed yarn of this invention in both the warp and the filling to produce an attractive fabric having 88 warp ends and 40 filling ends per inch (34.6 warp ends and 15.75 filling ends per centimeter). There are no known commercial offerings wherein an acetate or a polyester slubbed yarn is used in both the warp and the filling. It is assumed that this condition exists because the appeal and performance of such fabrics is not in keeping with the high cost of their production.

These, and other yarns of this invention, have the utmost utility in the production of silk-like fabrics. It has been reliably established that silk experts cannot consistently distinguish fabrics made from these slubbed yarns from comparable all-silk fabrics. In view of the improved weaving results of slubbed yarns of this invention, the variety of yarns of consistent quality that can be produced, and the superior appearance, handle and performance of fabrics produced from them, their superiority is clearly established.

What is claimed is:

1. In a process for producing slubbed yarn that includes the steps of continuously feeding a multifilament yarn to a supply jet and forwarding the yarn in a first high velocity fluid stream onto one area of a foraminous member, directing a second high Velocity fluid stream from a slub jet against another area of the foraminous member adjacent the first stream to form a turbulent zone between the first and second streams, forming and consolidating slubs in the yarn by continuously withdrawing the yarn from the foraminous member through the turbulent zone and through the slub jet in a direction countercurrent to the second stream, the improvement of which comprises the step of:

forming said turbulent zone by directing said streams against areas of said foraminous member which have different porosities.

2. The process of claim 1 wherein said first stream is directed against one area of the foraminous member which has a lower porosity than the area against which the second stream is directed.

3. In a yarn treating apparatus including a feed jet for forwarding the yarn in a first high velocity fluid stream along a path, a foraminous member positioned across the path so that the yarn is deposited on one area of the member and fluid passes therethrough, a slub jet positioned adjacent said feed jet for directing a second high velocity uid stream against said member adjacent said one area, means for withdrawing the yam from said member through said slub jet in a direction countercurrent to said second uid stream, wherein the improvement comprises: said one area having a porosity less than the porosity of said foraminous member.

4. In a yarn treating apparatus including a feed jet for forwarding the yarn in a first high velocity fluid stream, along a path, a foraminous member having upper and lower surfaces positioned across the path so that the yarn is deposited on one area of the upper surface of the member, a slub jet positioned adjacent said feed jet for directing a second high velocity fluid stream against said member adjacent said one area, means for withdrawing the yarn from said member through said slub jet in a direction countercurrent to said second uid stream, wherein the improvement comprises: a flow restricting element attached to the lower surface of said foraminous member, said element coinciding with said one area.

5. The apparatus of claim 4 wherein said element is impervious.

6. The apparatus of claim 4 wherein said member and said element are screens.

7. The apparatus of claim 4 wherein said member is a screen, said element being a plate having a plurality of holes therethrough.

8. A variable denier multilament yarn comprising portions of a substantially uniform denier and characterized by having at least 200 slubs per 1,000 yards, about 40 to approximately of said slubs having a segment with a denier ratio greater than about 7, about 1 to ap-` proximately 10% of said slubs having a segment with a denier ratio greater than about 25%, less than 1% of said slubs having a segment with a denier ratio greater than about 40.

9. A variable denier multilament yarn comprising portions of a substantially uniform denier and characterized by having at least slubs per 1,000 yards, about 40 to approximately 95% of said slubs having a segment with a denier ratio greater than about 7, about 1 to approximately 10% of said slubs having a segment with a denier ratio greater than about 25%, about 1% of said slubs having a segment with a denier ratio greater than about 40.

10. The yarn as defined in claim 9, said yarn consisting of polyamide units, said units being predominately units of bis(4aminocyclohexyl) methane and dodecanedioic acid.

References Cited UNITED STATES PATENTS 3,116,589 1/1964 Edwards et al 57-157 3,174,271 3/1965 Edwards et al 57-140 3,296,785 1/ 1967 Hardy 57-34 JOHN PETRAKES, Primary Examiner U.S. Cl. X.R. 

